Electrical bus structure



July 26, 1949. J. w. MYERS ELECTRICAL BUS STRUCTURE 2 Sheets-Sheet 1 Filed March 25, 1946 INVENTOR. dfll/A/ W/LLMM All [E5 July 26, 1949. J. w. MYERS 2,477,523

ELECTRICAL BUS STRUCTURE Filed March 25, 1946 2 Sheets-Sheet 2 rsupzmruz: as: m? 066E555 aw INVENTOR. dOHN W/LLMM M7565 ZM/Q Patented July 26, 1949 ELECTRICAL BUS STRUCTURE.

John William Myers, Balboa Island, Calif., as-

signor to Zinsmeyer Company, Los Angeles,

Calif.

Application March 25, 1946, Serial No. 656,797

1 Claim. 1

This invention relates to panel boards, switch boards, and similar electrical service installations such as employed in factories, theatres, and other installations for the distribution of electricity to the various circuits. More specifically, the present invention relates to the bus structure employed in such switchboards and panel boards for the distribution of electrical current from the current supply cables to the various switches and circuit breakers which control the circuits or to any other electrical instruments or devices which are commonly mounted in switchboards and panel boards.

In supplying electric power to the average factory, for example, the current is delivered to a central switchboard where the current is received by bus bars for further distribution within the switchboard. The bars usually extend in parallel, spaced relation through the switchboard and are connected to the switches and circuit breakers by smaller copper bars known in the art as jumpers. The jumpers are attached to the bus bars by screws or bolts, suitable holes being drilled in the jumpers and threaded holes provided in the bus bar to receive the screws.

In a switchboard having a large number of closely spaced switches and circuit breakers, many jumpers are required to conduct the current from the bus bars to the switches. This necessitates drilling and tapping many holes in the bus bars. The common practice has been to drill and tap the bus bar material along the center line at closely spaced, equidistant centers before the bars are mounted in the switchboard. The drilled and tapped bus bar material is kept in stock for future use even though the exact number and location of. switches in a future switchboard is not known.

Bus bar material may be also purchased with the tapped holes provided at given spacings. Al= though this practice often results in the drilling and. tapping of as many as fifty to seventy-five per cent more holes than are generally required, it has proven more economical to follow this practice than to machine each set of bus bars to fit a particular switch or panel board. Even though the holes are provided on closely spaced centers, it often occurs in the assembly of a switchboard that some of the predrilled holes do not line up properly with some of the switches thereby requiring the drilling and tapping of additional holes in addition to those already provided.

As the current carrying capacity of a bus bar depends on the cross sectional area of the bar, the metal removed by drilling holes for the jumpers reduces the capacity of the bar, particularly when a large number of closely spaced holes are drilled in the bar.

Another difficulty encountered in the practice outlined above is the changing of a switchboard after the board has been installed and in use. It is often necessary to add switches and change the location of switches to accommodate additional circuits which may necessitate the drilling and tapping of additional holes in the bus bars. After drilling and tapping a hole, the burrs around the hole must be carefully removed to insure full contact between the bus bar and jumper.

It is accordingly an object of the present invention to provide a novel bus bar and jumper arrangement whereby the provision of holes in the bus bar is entirely eliminated.

A further object of my invention is the provision of a bus bar and jumper arrangement whereby the jumper may be connected to the bus bar at any desirable location without drilling and tappin holes in the bar.

Another object of this invention is the provision of a bus bar and jumper arrangement which will permit changing the position of the jumper in relation to the bus bar in an extremely simple manner.

Still another object of my invention is the provision of a bus bar of greater current carrying capacity.

A further object of my invention is the provision of a novel clamping means for attaching a jumper to the bus bar of the present invention.

Further objects and advantages will become apparent in the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is a front elevational view of a panel board unit, a portion of the front panel bein broken away to expose the bus bars to which the resent invention relates.

Fig. 2 is a horizontal sectional view taken on the line 2-2 of Fig. 1.

Fig. 3 is an enlarged end view of one of the bus bars shown in Fig. 1 looking in the direction of the arrow 3 of Fig. 1.

Fig. 4 is an enlarged, transverse sectional View showing the manner in which a branch jumper is clamped to one of the bus bars.

Fig. 5 is a fragmentary, elevational View of the structure shown in Fig. 4.

Fig. 6 is a perspective view of one of the clamps used in connection with the bus bar of my invention.

Fig. 7 is a graph showing the results of a test conducted for the purpose of comparing the current carrying capacity of the bus bar of my invention with that of the conventional bus bar.

Referring specifically to the drawings, a preferred form of bus bar it] of my invention is shown in Fig. 1 in connection with a typical panel board unit 12, it being understood that the bus bar structure of the present invention may be used in many different electrical installations other than the panel board l2. The unit l2 includes side panels I3 to which a back panel id is fixed as shown in Figs. 1 and 2. Removably fixed on the front of the unit l2 by screws It are cover panels I? and lil. Provided on the inside surface of the back panel 14 are posts l for supporting a frame 25.

The frame 26 includes a pair of vertical channel members iii to which mounting plates '22 are welded. The plates 22 are bolted to the posts l5 thereby supporting theframe within the unit i2. Fixed to the channel members El are angle brackets :25 for supporting circuit breakers 25 as seen in Fig. 2. Extending transversely between the channel members 2| are bars til of electrical insulating material, one of the bars being provided at the top or the frame 25 and another at the bottom as shown in Fig. 1.

The bus bars iii are mounted on the insulating bars 38 and are coextensive with the frame 2i! as shown in Fig. 1. Each of the bus bars it includes a pair of identical copper bals 35 spaced to provide a slot 33 of uniform width and coextensive with the bus bars 10.

Provided at each end of each of the bars it is a clamp member iii as shown in Figs. 1, 3, and 6. Each of the clamp members it, as seen in Fig. 6, is formed to provide a rectangular plate ii having a central'square hole 32. Opposite edges of the plate ii are bent to form stifiening ribs 33. Downstruck at each of the four corners of the member ii? are projections 65.

The bus bars l5 are clamped to the insulating bars so as shown in Fig. 3. Bolt holes 65 are drilled through the bars 35 at the desired center line of each of the bus bars Iii. Carriage bolts at are inserted through the clamps 40, slots 35, and hole #55. Tightening of the bolts clamps the bars 35 of the bus bars l5 securely between the clamp members All and the insulating bars as. The projections as of the clamp members til engage outside edges of the bars 35 thereby positioning and retaining the bars 35 against outward movement. The bolt 45, as seen in Fig. 3, prevents the bars 35 from moving toward each other, the bolts 55 and projections 44 of the clamp members ii! coacting to positively retain the bars 35 in predetermined, spaced relation.

Mounted on upper ends of the bus bars it, as seen in Figs. 1 and 3, are cable lugs bolted to the bars ill by bolts 5! (see Fig. 1) the latter passing through the slots 35. The lugs receive current supply cables (not shown) which supply current to the bus bars it.

From the bus bars it, electrical current is distributed to the various circuit breakers '26 by jumpers '55 as shown in Figs. 2, i, and 5. The jumpers 55, like the bars 35 of the bus bars iii,

are made of copper and are secured to the bus bars H), as shown in Fig. 4, by two of the clamp Tightening of the carriage bolt 56 clamps the bars 35 and the jumper 55 firmly and evenly together thereby insuring full electrical contact. Wherever jumpers are clamped to the bus bars it, the clamps i0 retain the bars 35 in proper spaced relation as a result of engagement of the projections 44 of each of the clamp members as with outside edges of the bars 35.

The location of any of the jumpers 55 in relation to the bus bar it may be readily changed by loosening the bolt 56 and sliding the jumper 55 and clamp members 43 along the bus bar to the desired location and tightening the bolt 55.

Reference is now made to the graph shown in Fig. 7. The curves A and B indicate the results of a comparative test conducted in the following manner:

Two bus bars, one of conventional design and one of equal length made in accordance with the bar iii of the present invention, were connected to a supply of electrical current of 250 amperes. The conventional bus bar was one quarter inch thick by one inch in width. The bar Ii] used in the test included two, one quarter inch by one half inch bars, the amount of material in the conventional bar being equal to the amount of material in the bars comprising the bar 15. Therrnocouples were attached to the center of each of the bars being tested and temperature readings were taken at the intervals indicated on the graph of Fig. 7.

The curve A along points al to at inclusive indicate the temperature of the conventional bus taken at the time increments indicated on the graph. The points hi to D3 inclusive of curve B indicate the successive temperature readings of the bus of my invention.

It will be noted on the graph that aiter one hour, the temperatures of the two bars leveled ,ofi, the conventional bar having risen nineteen degrees centigrade while the bar it rose but eleven and five tenths degrees. This test indicates that the bus bar of the present invention will carry more current than the conventional type of equal cross-sectional area without exceeding the permissable rise in temperature.

One reason for the superior performance of the bus bar It is the absence of the holes'which are necessary in the conventional bar.

Another reason for the greater efficiency of the bus bar of the present invention, as indicated on the graph of Fig. 7, is the greater heat radiating area of the bar it as compared with the area of a conventional bar.

Although I have shown and described but one preferred embodiment of the structure of my invention, it is understood that various modifica tions and changes'may be made therein without departing from the spirit of the invention or the scope of the appended claim.

I claim as my invention:

A clamp for securing a jumper to a pair of parallel, spaced bars used as a single bus bar, said clamp comprising, identical clamp members, each having projections extending from a clamping face thereof, the projections on one of said members engaging edges of said spaced bars to prevent rotation of said member relative to said bars and to retain said bars improper spaced relation, a jumper disposed between said bars and the other of said pair of said clamp members, and a central bolt passing through said clamp members andsaid jumper, the projections-on one of said clampmembers engaging edge portions of said jumper preventing rotation of said member relative to said jumper, the length of said projections being less than the thickness of said jumper thereby permitting rotation of said,

jumper and said clamp member without contact of said projections with said bus bars.

JOHN WILLIAM MYERS.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number 6 UNITED STATES PATENTS Name Date Jacobs Mar. 8, 1927 Frank June 22, 1937 Novak Nov. 4, 1941 FOREIGN PATENTS Country Date Norway July 22, 1935 

